0.19.0

Breaking

• Updated enum serialization/deserialization in the JSON 0.6 serializer to match
  apiaryio/api-elements#28
• Element.children and Element.recursiveChildren now return ArraySlice
  instead of an ArrayElement.
• ArrayElement.filter and ArrayElement.find* now return ArraySlice
  instead of an ArrayElement.
• The first, second and last methods on ArrayElement are now properties
  instead of methods.
• ObjectElement.filter now returns an ObjectSlice instead of an
  ObjectElement.
• When providing multiple element names to Element.findRecursive you must
  call freeze on the element beforehand so that the element has access to the
  parent of the element.

Enhancements

• Introduced JSDoc documentation to public interfaces
• Element now contains a freeze method to freeze and prevent an element
  from being mutated, this also adds a parent property on all child elements.

Bug Fixes

• Handle serializing key-value pair without value
• Deserialize dataStructure containing an array correctly